This application is based on and incorporates herein by reference Japanese Patent Applications No. 2000-203783 filed Jul. 5, 2000 and 2001-174166 filed Jun. 8, 2001.
The present invention relates to an anti-theft system for vehicles, and more particularly to an anti-theft system for vehicles having a function of allowing starting of an engine by remote control.
Various types of anti-theft systems are known, for preventing vehicle thefts by any unauthorized operation including, for example, opening a door or a trunk lid with any illegal means other than the proper key.
Such an anti-theft system will enter into an anti-theft guard mode, when a user turns off the ignition switch, pulls the key out and then locks all doors. In the guard mode, any unauthorized operation is monitored. If an unauthorized operation is performed, the system enters into an alarm mode to sound a horn, and/or flash on and off hazard lamps. The guard mode is released only when the user unlocks the door with the proper key to enter a guard-free mode. Thus, a vehicle is in either one of the anti-theft (protection) modes, that is, the guard mode, the guard-free mode or the alarm mode.
However, the conventional anti-theft system is often set so as to enter from the guard mode into the alarm mode when the power supply has been once shut down and then recovered, other than the unauthorized operations. This is for causing the system in the guard mode to enter into the alarm mode, by determining an unauthorized removal of a battery by someone illegally, when the car battery is removed to stop operating the anti-theft system, and then is re-connected to start operating again the system.
That is, when the operation voltage supplied to the anti-theft system decreases below the lower limit voltage to be supplied for the system to operate, the anti-theft system stops operating. When the power is restored over the lower limit voltage to be supplied to the system, the system is re-initialized to start operating. In this case, the operation mode (protection mode) prior to stopping operation (prior to initialization) may be stored. When the system is initialized to start operating again, the operation mode is checked. If the operation mode prior to initialization is the guard-free mode, then the system will continue the guard-free mode. If the protection is the guard mode, then the system enters into the alarm mode to generate an alarm.
The cause of decrease of the operation voltage supplied to the anti-theft system is not limited to the removal of the battery. For example, cranking for starting the engine may cause a momentary voltage drop of the battery voltage below the lower limit value of the operation voltage. However the engine is started in the normal usage after the user uses the proper key to open the door to release the guard mode to the guard-free mode. If a momentary drop of battery voltage caused by starting the engine may result in an initialization of the anti-theft system, the guard-free mode is held because the operation mode before initialization is guard-free mode. Therefore, a voltage drop of the battery caused by cranking for starting the engine may not trigger the alarm mode.
However, in an anti-theft system, a user may use a remote engine starter to warm up the engine in advance, in such a manner as the user transmit data from a transmitter to warm up the engine from a remote place. The system may enter into the alarm mode, even though the operation is not a fraudulent action.
More specifically, when a user attempts to start the engine from a remote place with a remote engine starter device, the operation mode of the vehicle is in general the guard mode. In such a situation, if the user starts the engine with the remote engine starter, the battery voltage will hazardously decrease to initialize the anti-theft system. If initialized inadvertently, because the operation mode before initialization is in the guard mode, the anti-theft system enters into the alarm mode to generate an alarm when the battery voltage is restored to resume the operation of the anti-theft system. When the battery becomes weak, if the remote engine starter is used to start the engine, then the cranking until the engine completely starts running will result in a decrease of the operation voltage for the anti-theft system below the lower limit value. As a result, the anti-theft system will alarm each time the engine is started.
On the other hand, when a false alarm is triggered, a keyless entry system can be used to release the door lock, for example, to cause the anti-theft system to enter into the guard-free mode to stop the alarm. However, in this case the security may be lowered.
There are various types of unauthorized operations of the vehicle as well as various methods for detecting such operations. For example, for detecting an intruder attempting to intrude into the vehicle compartment by breaking a glass window, an intruder sensor is used in general by making use of ultrasonic or electromagnetic waves. Such an intruder sensor transmits ultrasonic or electromagnetic waves and measures the difference in frequencies between the transmission and the waves reflected from the object in the compartment. If the differential changes, an intruder is determined to be present. Such a sensor is affixed to for example the rear view mirror.
For detecting someone moving the vehicle by a towing truck (wrecker), an inclination sensor (e.g., a gyro sensor) is used for detecting the inclination of vehicle. This is because the vehicle is inclined when the towing truck raises an end part of the vehicle. The inclination sensor detects, based on the amount of inclination, that the vehicle is transported.
However, when the engine is started by using the remote engine starter device in the guard mode, the intruder sensor and inclination sensor may erroneously detect intruder or inclination, caused by factors including the vibration of vehicle due to the engine running, although no unauthorized operation has been made. During driving the starter motor immediately after starting the engine, the vibration of vehicle is large in particular. Thus, there is a large possibility of making a fault alarm.
When using an intruder sensor making use of ultrasonic waves, a false alarm may be triggered due to the air flow in the compartment by the air conditioner which is turned on when starting engine, for example, during the guard mode, other than the vibration of vehicle. In addition, the intruder sensor making use of electromagnetic waves may be jammed by the influence of surge noises generated at the time of driving the starter motor.
The present invention has an object to provide an anti-theft system for vehicles, which will not be triggered erroneously when no unauthorized action has been taken, at the time of starting an engine remotely by means of a remote engine starter device.
According to the present invention, an anti-theft system for vehicles is mounted on a vehicle having a remote starter control device for starting an engine in response to a turning-on instruction transmitted from an external transmitter. An operation mode of the system is set into either one of a guard mode and a guard-free mode in response to an operation of a user, and the operation mode is stored in an operation mode storage device. An alarm is generated outwardly, when an unauthorized operation of a vehicle is detected by an improper operation detection sensor under the condition that the operation mode is the guard mode.
The system determines whether the remote starter control device is operating and prevents the alarm if the remote starter control device is operating at the time of starting the system operation.
The system checks whether the remote starter control device is in operation and reduces detection sensitivity of the unauthorized operation sensor if the device is determined to be in operation.
The system checks whether the remote starter control device is in operation, and prevents the alarm if the unauthorized operation sensor detects the unauthorized operation under the condition that the remote engine starter control device is in operation.